Foundry's petard that TLC links to is a 17th-century ECW model, and is a different sort of thing entirely. The dictionaries mostly seem to say that "petard" only originated in the 16th century, so the WRG lists may have the wrong word for the C15th Burgundian powder-pot chuckers.

What the "Burgundians" are supposed to be using is a firepot proto-grenade, probably not too different from the Crusade-era ones discussed at link . There are a few in mediaeval illustrations and the reconstruction in Terry Wise's Osprey "Wars of the Roses" claims to be based on "Royal MS 14, E.IV" which is available at link but I don't know what page. See the figure on the left at

for the kind of thing.

I don't know of any figures but they should be easy to convert – almost any armoured figure with a blob of putty in his hand for the "grenade".